Climate and environmental data gaps in interpreting proxy records

Proxy records – like tree rings, coral cores, or ice cores – provide indirect evidence for understanding past environmental and climatic conditions.

In the Great Barrier Reef, these records are derived from cores from coral colonies, coral reefs and sediment deposition areas, offering valuable insights into the Reef’s historical disturbances.

The production of reliable and long-term environmental and climate data records is essential. These records include sea surface temperature, river discharge, sea-level change, river avulsion, pollutant loads, and storms.

This long-term data provides an enhanced perspective on the pressures marine ecosystems have encountered, which can then be linked to similar long-term records of coral health, such as coral reef accretion and coral geochemistry.

Decoding reef history with proxy records

We are producing new environmental and climate proxy records to better understand the Reef's disturbance history and long-term ecosystem evolution. This work also documents the environmental and climate history of the north Queensland region.

This research spans multiple projects and involves the compilation, synthesis and curation of existing records with some new investigations.

Sea-level change records:

• Analysed sea-level proxies (e.g., oysters, coral microatolls) to produce a record of sea-level change for the Australian region over the past 20,000 years. This links with coral reef growth and evolution records and historical Indigenous movement across Australia.

Records of land-use change and historical river discharge:

• Compiled annual records from 1860 to 2019 to identify major modifications in river basins to link with changes in hydrology and pollutant levels.

• Luminescent lines in coral cores provide proxies for reconstructing river discharge history over hundreds of years.

Records of longer-term coral health:

• Coral accretion and morphology records from reef flat sediment cores offer insights into longer-term coral health, reef evolution, and disturbance regimes.

• These records help provide a different perspective of coral reef growth over thousands of years.

Coral geochemistry proxy records:

• Coral geochemistry proxy records reveal environmental and climatic changes in the Great Barrier Reef catchment and lagoon.

• Rare earth elements in coral skeletons show great promise to understand changes in sediment exposure, quantifying impacts from increased riverine inputs, resuspension, or dredging.

Bridging the gap to understand ecosystem evolution

Our research bridges the gap between long-term proxy records and current environmental data, providing managers and policymakers with a clearer understanding of the Great Barrier Reef's history and long-term ecosystem evolution.

By analysing coral and sediment cores, we can accurately link changes in marine environments to their direct causes. This comprehensive approach allows us to:

• Document the history of coral growth on the Great Barrier Reef

• Quantify changes in river discharge to the Great Barrier Reef to understand changes in the exposure of terrestrial runoff on marine ecosystems and to develop long-term flood records for Queensland.

• Provide an independent line of evidence to quantify how sediment loads discharged to the Great Barrier Reef have changed over time to validate modelling outputs.

• Provide critical long-term data for better decision-making and effective management strategies.

These insights are essential for protecting the reef and ensuring its resilience against future disturbances. It informs policies that promote sustainable practices and conservation efforts and helps us understand the broader climate variability of our region.